The aim of the project is to study the effect of 1,25 dihydroxy Vitamin D3 and calcitonin on fracture healing. Although breaking strength is the basic criteria for evaluating the fracture union in this proposal, we are also proposing to assess fracture healing by the non-destructive and non-invasive method of driving point mechanical impedance. The experimental model for this investigation is based on the femoral fracture in rats. The animals will be divided into four groups of which one is the control. The three test groups will receive 1,25(OH)2D3, calcitonin, and both 1,25(OH)2D3 and calcitonin. The fracture will be monitored radiographically. The animals will be sacrificed at weekly intervals over a ten week period. A biomechanical as well as morphological evaluation will be made of the fractured bones. Biomechanical studies will consist of determining the driving point mechanical impedance and determining the breaking strength. The morphological investigation comprises the study of the disuse, histology and cell counting and ash content. That 1,25(OH)2D3 is a calcium mobilizing hormone and calcitonin is an inhibitor of bone resorption have already been validated by several investigators. Also, the impedance technique instrumentation has been validated by several researchers on intact bones. Therefore, the prime object of this investigation is to apply these facts in the influence and assessment of fracture healing.